Adhesive resins for wafer bonding

ABSTRACT

An adhesive bonding method that includes bonding a handling wafer to a front side surface of a device wafer with an adhesive comprising N-substituted maleimide copolymers. The device wafer may then be thinned from the backside surface of the device wafer while the device wafer is adhesively engaged to the handling wafer. The adhesive can then be removed by laser debonding, wherein the device wafer is separated from the handling wafer.

BACKGROUND

Technical Field

The present disclosure relates generally to adhesives employed in waferbonding.

Description of the Related Art

Temporary wafer bonding/debonding is an important technology forimplementing the fabrication of semiconductor devices, photovoltaicdevices, and electrical devices of micron and nanoscale. Bonding is theact of attaching a device wafer, which is to become a layer in a finalelectronic device structure, to a substrate or handling wafer so that itcan be processed, for example, with wiring, pads, and joiningmetallurgy. Debonding is the act of removing the processed device waferfrom the substrate or handling wafer so that the processed device wafermay be employed into an electronic device. Some existing approaches fortemporary wafer bonding/debonding involve the use of an adhesive layerplaced directly between the silicon device wafer and the handling wafer.When the processing of the silicon device wafer is complete, the silicondevice wafer may be released from the handling wafer by varioustechniques, such as by exposing the wafer pair to chemical solventsdelivered by perforations in the handler, by mechanical peeling from anedge initiation point or by heating the adhesive so that it may loosento the point where the silicon device wafer may be removed by sheering.

SUMMARY

In one embodiment, a method for adhesive bonding in microelectronicdevice processing is provided that includes bonding a handling wafer toa front side surface of a device wafer with an adhesive comprisingN-alkyl or N-aryl maleimide copolymers, wherein the co-monomers includestyrenic monomers, norbornene derivatives, vinyl ethers and maleicanhydride; and thinning the device wafer from the backside surface ofthe device wafer while the device wafer is adhesively engaged to thehandling wafer. After the device wafer has been thinned, the adhesivemay be removed by laser debonding, wherein the device wafer is separatedfrom the handling wafer. In this instance, the co-polymer can be definedas polymers having at least two different monomer units. In someexamples, the polymer may comprise more than two different monomerunits. In one example, the maleimide copolymer is provided bystyrene-N-substituted maleimide copolymer. In another example, thecopolymer is a vinyl ether-N-substituted maleimide copolymer. In yetanother example, the copolymer is provided by norbornene-N-substitutedmaleimide copolymer. These polymers may have additional monomer unitssuch as maleic anhydride.

In one embodiment, the adhesive bonding method may include bonding ahandling wafer to a front side surface of a device wafer with anadhesive comprising N-substituted maleimide copolymers. The device wafermay then be thinned from the backside surface, while the device wafer isadhesively engaged to the handling wafer. The adhesive can then beremoved by laser debonding, in which the device wafer is separated fromthe handling wafer. In some examples, the N-substituted maleimidecopolymers is a vinyl ether/maleimide copolymer. In some examples, theN-substituted maleimide copolymer comprises poly(dodecyl vinylether-co-phenylmaleimide).

In another aspect of the present disclosure, a wafer bonding adhesive isprovided. In one embodiment, the wafer bonding adhesive may be composedof styrene-maleimide copolymers dissolved in solvents commonly used inelectronic industry and wherein the polymer is thermally stable attemperatures greater than 300° C., and has a glass transitiontemperature that is tunable within a range of 50° C. to 225° C.

In yet another embodiment of the present disclosure, a method of forminga wafer bonding adhesive is provided that includes providing a solventcommonly used in electronic industry, and dissolving styrene maleimidecopolymers in the solvent, wherein molecular weight of thestyrene-maleimide copolymers is selected to tune a glass transitiontemperature of the adhesive.

In yet another embodiment of the present disclosure, a method of forminga wafer bonding adhesive is provided that includes providing a solventcommonly used in electronic industry, and dissolving styrene maleimidecopolymers in the solvent, wherein the functional groups in thestyrene-maleimide copolymers are selected to tune the glass transitiontemperature of the adhesive.

In yet another embodiment of the present disclosure, a method of forminga wafer bonding adhesive is provided that includes providing a solventcommonly used in electronic industry, and dissolving vinylether-maleimide copolymers in the solvent, wherein molecular weight ofthe styrene maleimide copolymers is selected to tune a glass transitiontemperature of the adhesive.

In yet another embodiment of the present disclosure, a method of forminga wafer bonding adhesive is provided that includes providing a solventcommonly used in electronic industry, and dissolving vinylether-maleimide copolymers in the solvent, wherein the functional groupsin the vinyl ether-maleimide copolymers are selected to tune the glasstransition temperature of the adhesive.

A casting solvent can be used to prepare adhesive composition. Thechoice of solvent is governed by many factors not limited to thesolubility and miscibility of resist components, the coating process,and safety and environmental regulations. It is also desirable that thesolvent possess the appropriate volatility to allow uniform coating offilms yet also allow significant reduction or complete removal ofresidual solvent during the post-application bake process. Solvents maygenerally be chosen from ether-, ester-, hydroxyl-, andketone-containing compounds, or mixtures of these compounds. Examples ofappropriate solvents include cyclopentanone, cyclohexanone, lactateesters such as ethyl lactate, alkylene glycol alkyl ether esters such aspropylene glycol methyl ether acetate, alkylene glycol monoalkyl esterssuch as methyl cellosolve, butyl acetate, 2-ethoxyethanol, and ethyl3-ethoxypropionate. Preferred solvents include ethyl lactate, propyleneglycol methyl ether acetate, and mixtures of ethyl lactate and ethyl3-ethoxyproprionate. The above list of solvents is for illustrativepurposes only and should not be viewed as being comprehensive nor shouldthe choice of solvent be viewed as limiting the invention in any way.

In another aspect of the present disclosure, the composition of a waferbonding adhesive is provided in which the adhesive composition comprisesa maleimide copolymer dissolved in solvents that is thermally stable attemperatures greater than 300° C., and a glass transition temperaturethat is tunable within a range of 50° C. to 225° C. In some embodiments,the maleimide copolymer is an N-substituted maleimide copolymer. In someexamples, the N-substituted maleimide copolymer is a vinylether/maleimide copolymer. In at least one example, the N-substitutedmaleimide copolymer may be poly(dodecyl vinyl ether-co-phenylmaleimide).The maleimide copolymer composition may also be is selected from thegroup consisting of styrene-N-alkylmaleimide copolymer,Styrene-N-arylmaleimide copolymer, vinyl ether-N-alkylmaleimidecopolymer, vinyl ether-N-arylmaleimide copolymer, and combinationsthereof.

BRIEF DESCRIPTION OF DRAWINGS

The disclosure will provide details in the following description ofpreferred embodiments with reference to the following figures wherein:

FIG. 1 is a side cross-sectional view of a semiconductor substrate thatmay be employed as a device wafer in a method of forming a semiconductordevice that employs adhesive bonding of the device wafer to a handlingwafer as part of a wafer thinning sequence, in accordance with thepresent disclosure.

FIG. 2 is a side cross-sectional view of forming semiconductor deviceson a front surface of the device wafer, in accordance with oneembodiment of the present disclosure.

FIG. 3 is a side cross-sectional view of bonding a handling wafer to thefront surface of the device wafer through an adhesive, in accordancewith one embodiment of the present disclosure. The adhesive may be oneof a styrene maleimide copolymer; vinyl ether maleimide copolymer and acombination thereof.

FIG. 4 is a side cross-sectional view depicting thinning the backsidesurface of the device wafer, in accordance with one embodiment of thepresent disclosure.

FIG. 5 is a side cross-sectional view depicting patterning the backsidesurface of the thinned device wafer, in accordance with one embodimentof the present disclosure.

FIG. 6 is a side cross-sectional view depicting laser debonding toablate the adhesive, and to remove the handling wafer from the devicewafer, in accordance with one embodiment of the present disclosure.

FIG. 7 is a flow chart illustrating another approach for performingsemiconductor containing handler substrate bonding and de-bonding inaccordance with other exemplary embodiments of the present disclosure.

FIG. 8 is a schematic diagram illustrating bonding and de-bonding of asemiconductor containing device substrate to a silicon containinghandler substrate, in accordance with exemplary embodiments of thepresent disclosure.

FIG. 9A is schematic diagrams illustrating a first pattern of applyingthe laser light to a top surface of the semiconductor containing handlersubstrate in accordance with exemplary embodiments of the presentdisclosure.

FIG. 9B is schematic diagrams illustrating a second pattern of applyingthe laser light to a top surface of the semiconductor containing handlersubstrate in accordance with exemplary embodiments of the presentdisclosure.

FIG. 10 is a schematic diagram illustrating a scanning laser de-bondingsystem in accordance with exemplary embodiments of the presentdisclosure.

FIG. 11 is a plot of complex viscosity (Pa sec) as a function oftemperature for polymeric adhesives composed of styrene maleimidecopolymers, in accordance with one embodiment of the present disclosure.

FIG. 12 is a plot of illustrating complex viscosity (Pa sec) as afunction of temperature for polymeric adhesives composed of vinylether-maleimide copolymers.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Detailed embodiments of the claimed structures and methods are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely illustrative of the claimed structures and methods that maybe embodied in various forms. In addition, each of the examples given inconnection with the various embodiments are intended to be illustrative,and not restrictive. Further, the figures are not necessarily to scale,some features may be exaggerated to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the methods and structures of the present disclosure. Referencein the specification to “one embodiment” or “an embodiment” of thepresent principles, as well as other variations thereof, means that aparticular feature, structure, characteristic, and so forth described inconnection with the embodiment is included in at least one embodiment ofthe present principles. Thus, the appearances of the phrase “in oneembodiment” or “in an embodiment”, as well any other variations,appearing in various places throughout the specification are notnecessarily all referring to the same embodiment.

For purposes of the description hereinafter, the terms “upper”, “lower”,“right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, andderivatives thereof shall relate to the embodiments of the disclosure,as it is oriented in the drawing figures. The term “positioned on” meansthat a first element, such as a first structure, is present on a secondelement, such as a second structure, wherein intervening elements, suchas an interface structure, e.g. interface layer, may be present betweenthe first element and the second element. The term “direct contact”means that a first element, such as a first structure, and a secondelement, such as a second structure, are connected without anyintermediary conducting, insulating or semiconductor layers at theinterface of the two elements.

In some embodiments, the methods, compositions and structures disclosedherein provide low cost, thermoplastic materials that can be used asadhesives in temporary bonding of thin layers of semiconductor material,such as silicon containing material layers, to wafer handler substrates.As used herein, the term “thin” denotes a thickness of 5 microns to 10microns. In some embodiments, the methods, compositions and structuresdisclosed herein provide an adhesive that can be used in method thatemploy laser debonding. Laser debonding is one method that is typicallyemployed in layer transfer techniques used in microelectronicproduction, such as the formation of microelectronics employingsilicon-containing substrates.

Typically, in laser debonding, a polyimide material is used as theadhesive connecting the device wafer to a handling wafer, whereinablating the polyimide adhesive employs a deep UV excimer laser thatdebonds the device wafer from the handling wafer. The handling wafer maybe a coefficient of thermal expansion (CTE) matched glass plate. In someexamples, the polyimide that is used as the adhesive is known in theindustry by tradename HD3007, which may be available from HDMicrosystems, Inc. It has been determined that one disadvantage of usinga polyimide adhesive material as the adhesive in wafer bonding methodsin microelectronics device manufacturing is the relatively highprocessing temperature that is required to convert the polyimideprecursor, i.e., polyamic acid, to a fully imidized polyimide beforecompleting bonding of the handling wafer to the device wafer. Thetemperature range that is typically used to cure the polyimide toprovide imidization ranges 300° C. to 400° C. In addition, the nature ofa polyimide polymer is usually relatively stiff and rigid such that thepolymer requires a high temperature to soften and bond to the handlingwafer. The high temperatures required for both steps can do damage tosensitive devices that are included in the device wafer. Further, thehigh temperatures required for curing the polyimide for imidization andto soften the polyimide for softening can cause stresses in the devicewafer that induce warping in the device wafer after cooling.Additionally, in order to remove polyimide residues that remain afterdebonding long soak times in strong hot solvents, such asN-methylpyrrolidone (NMP) and dimethyl sulfoxide (DMSO), may berequired.

In some embodiments, the methods, structures and compositions providedherein provide a set of adhesives that are low cost and have beendetermined to have good bond/debonding performance for adhesives atlower temperatures than prior commercially available adhesive used inwafer bonding without exhibiting squeeze-out phenomena.

In one embodiment, the present disclosure provides an adhesive composedof maleimide copolymers for wafer bonding. The adhesive composition issuitable for wafer bonding and laser debonding. The term “maleimide” asused to describe the maleimide component of the copolymers of thepresent disclosure is the chemical compound which has the followingchemical formula:

Maleimides also describes a class of derivatives of the parent maleimidewhere the H in the NH group is replaced with alkyl or aryl groups suchas a methyl or phenyl, respectively. The substituent can also be apolymer such as polyethylene glycol.

The maleimide monomer unit that may be employed in the copolymer andterpolymer compositions of the present disclosure include Monomers ofthe structural unit of the maleimide compound represented by the formula(I) may preferably include, for example, N-methyl maleimide, N-ethylmaleimide, N-n-propyl maleimide, N-i-propyl maleimide, N-t-butylmaleimide, N-Hexyl, N-dodecyl maleimide, N-octadecyl maleimide, N-phenylmaleimide, N-o-methylphenyl maleimide, N-p-isopropyl phenyl maleimide,N-phenyl-α-methyl maleimide, N-phenyl-α-chloromaleimide, N-cyclohexylmaleimide and N-benzyl maleimide.

In some embodiments, in which the maleimide copolymer is employed as anadhesive for wafer bonding/laser debonding applications, the maleimidecopolymer may have the composition of a styrene maleimide copolymer. Forexample, the styrene-maleimide copolymer composition may have thefollowing chemical formula:

Wherein R is an alkyl or aryl group and x,y are number of repeat units.

Terpolymers (and tetra-polymers) comprising these two units are alsoincluded in the group described as styrene maleimide copolymers that canbe used as adhesives in wafer bonding applications, in accordance withthe present disclosure.

In some embodiments, terpolymer suitable for adhesive applications hasthe following structure:

Wherein, R is alkyl or aryl group and x,y,z are number of repeat units.

The styrene-maleimide copolymers are typically thermally stable totemperatures of 300° C. and above. In one embodiment, the styrenemaleimide copolymers adhesives may have a glass transition temperature(Tg) that is tunable in a temperature range that can range from 50° C.to 220° C. In another embodiment, the styrene-maleimide copolymeradhesives may have a glass transition temperature (Tg) that is tunablein a temperature range that ranges from 90° C. to 205° C.

The glass transition temperature (Tg) may be tuned by employingdifferent compositions for the R-group in the above chemical formula forthe styrene maleimide copolymer. For example, to adjust the glasstransition temperature of the styrene maleimide copolymer, the R-groupof the chemical formula may incorporate different aryl (e.g., phenyl) oralkyl groups. The term “aryl”, as used to describe an aryl group, refersto any functional group or substituent derived from an aromatic ring, beit phenyl (C₆H₅), naphthyl (C₁₀H₈), thienyl (C₄H₄S), indolyl, etc. (seeIUPAC nomenclature). Each of the aforementioned aryl groups may beemployed as the R-group to tune the glass transition temperature (Tg) ofthe styrene maleimide copolymer. The term “alkyl”, as used hereindescribes an alkyl substituent in which an alkane is missing onehydrogen. An acyclic alkyl has the general formula C_(n)H_(2n+1). Acycloalkyl is derived from a cycloalkane by removal of a hydrogen atomfrom a ring and has the general formula C_(n)H_(2n−1). Typically analkyl is a part of a larger molecule. In structural formula, the symbolR is used to designate a generic (unspecified) alkyl group. The smallestalkyl group is methyl, with the formula CH₃—. Alkyls form homologousseries. The simplest series have the general formula C_(n)H_(2n+1).Alkyls include methyl (CH₃), ethyl (C₂H₅), propyl (C₃H₇), butyl (C₄H₉),pentyl (C₅H₁₁), hexyl (C₆H₁₃) and combinations thereof. Alkyl groupsthat contain one ring have the formula C_(n)H_(2n−1), e.g. cyclopropyland cyclohexyl. Each of the aforementioned alkyl groups may be employedas the R-group to tune the glass transition temperature (Tg) of thestyrene maleimide copolymer.

In some embodiments, styrene-maleimide copolymer adhesive compositionscan be provided that have a glass transition temperature (Tg) thatranges from 90° C. to 210° C. In some embodiments, the glass transitiontemperature (Tg) of the styrene maleimide copolymer adhesive may be95,100,105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165,170, 175, 180, 185, 190, 195, 200, and 205° C., as well as any range oftemperatures including at least two of the above noted values.Adjustment of the glass transition temperature of the styrene maleimideadhesives to the above temperature ranges allows for the adhesive to beapplied to a device wafer and then engaged, i.e., bonded, to a handlingwafer at a temperature that does not mechanically damage the adhesivelayer, the device wafer, and the carrier wafer.

The styrene maleimide copolymers can be made through simple free radicalco-polymerization of styrene and maleic anhydride monomers followed byfurther chemical reaction with amine containing molecules on the polymerto form imides. Through this two stage polymer synthesis andmodification, the styrene-maleimide copolymer adhesives can be tailoredto possess the desired optical, thermal and rheological properties.Further, in some embodiments, the materials can be synthesized throughdirect polymerization of styerene and N-alkyl or N-aryl maleimidemonomers if post-polymerization modification is desirable to avoid.

The styrene-maleimide copolymer adhesives are fully soluble and castablein common/safe solvents (e.g., PGMEA). The ability of styrene maleimidecopolymer adhesives to be dissolved in a solvent, such as propyleneglycol monomethyl ether acetate (e.g., PGMEA), provides that in waferbonding techniques that employ laser bonding to detach the temporarilyattached wafers that the adhesive may easily be removed from the wafersfollowing debonding by dissolving it in the same solvents.

In some embodiments, in which the maleimide copolymer that are employedas adhesives for wafer bonding/laser debonding applications inaccordance with the present disclosure has the composition of a vinylether-maleimide copolymer, the vinyl ether-maleimide copolymercomposition may have the following chemical formula:

wherein x, y are number of monomer units, R¹, R² groups are selectedfrom alkyl or aryl functionalities.

Terpolymers comprising these two units are also included in the group ofvinyl ether-maleimide copolymers that are disclosed herein for use asadhesives in wafer bonding applications. The third monomer may beselected from maleic anhydride and other functionalized maleimides. Insome embodiments the terpolymer suitable for adhesive applications hasthe following structure:

Wherein, R¹, and R² are independently selected form alkyl and arylgroups and x,y, z are number of repeat units.

The vinyl ether-maleimide copolymers are typically thermally stable totemperatures of 300° C. and above. In one embodiment, the vinyl ethermaleimide copolymers and terpolymers may have a glass transitiontemperature (Tg) that is tunable in a temperature range that can rangefrom 50° C. to 220° C. In another embodiment, the vinyl ether-maleimidecopolymer and terpolymer adhesives may have a glass transitiontemperature (Tg) that is tunable in a temperature range that ranges from90° C. to 205° C.

The glass transition temperature (Tg) may be tuned by employingdifferent compositions for the R¹, R²-groups in the above chemicalformula for the vinyl ether maleimide copolymer and terpolymers. Forexample, to adjust the glass transition temperature of the styrenemaleimide copolymer, the R¹, R²-groups of the chemical formula mayincorporate different aryl (e.g., phenyl) or alkyl groups. The term“aryl”, as used to describe an aryl group, refers to any functionalgroup or substituent derived from an aromatic ring, be it phenyl (C₆H₅),naphthyl (C₁₀H₈), thienyl (C₄H₄S), indolyl, etc. (see IUPACnomenclature). Each of the aforementioned aryl groups may be employed asthe R-group to tune the glass transition temperature (Tg) of the styrenemaleimide copolymer. The term “alkyl”, as used herein describes an alkylsubstituent in which an alkane is missing one hydrogen. An acyclic alkylhas the general formula C_(n)H_(2n+1). A cycloalkyl is derived from acycloalkane by removal of a hydrogen atom from a ring and has thegeneral formula C_(n)H_(2n−1). Typically an alkyl is a part of a largermolecule. In structural formula, the symbol R is used to designate ageneric (unspecified) alkyl group. The smallest alkyl group is methyl,with the formula CH₃—. Alkyls form homologous series. The simplestseries have the general formula C_(n)H_(2n+1). Alkyls include methyl(CH₃), ethyl (C₂H₅), propyl (C₃H₇), butyl (C₄H₉), pentyl (C₅H₁₁), hexyl,heptyl, octyl, nonyl, decyl and dodecyl and combinations thereof. Alkylgroups that contain one ring have the formula C_(n)H_(2n−1), e.g.cyclopropyl and cyclohexyl. Each of the aforementioned alkyl groups maybe employed as the R¹, and R²-groups to tune the glass transitiontemperature (Tg) of the styrene maleimide copolymer.

In some embodiments, vinyl ether-maleimide copolymer adhesivecompositions can be provided that have a glass transition temperature(Tg) that ranges from 90° C. to 210° C. In some embodiments, the glasstransition temperature (Tg) of the styrene maleimide copolymer adhesivemay be 95, 100. 105, 110, 115, 120, 125, 130, 135, 140, 145, 150,155,160, 165, 170, 175, 180, 185, 190, 195, 200, and 205° C., as well as anyrange of temperatures including at least two of the above noted values.Adjustment of the glass transition temperature of the vinyl ethermaleimide adhesives to the above temperature ranges allows for theadhesive to be applied to a device wafer and then engaged, i.e., bonded,to a handling wafer at a temperature that does not mechanically damagethe adhesive layer, the device wafer, and the carrier wafer.

The vinyl ether maleimide copolymers can be made through simple freeradical co-polymerization of vinyl ether and maleic anhydride monomers,followed by further chemical reaction with amine containing molecules onthe polymer to form imides. Through this two stage polymer synthesis andmodification, the vinyl ether-maleimide copolymer or terpolymeradhesives can be tailored to possess the desired optical, thermal andrheological properties. Further, in some embodiments, the materials canbe synthesized through direct polymerization of vinyl ether and N-alkylor N-aryl maleimide monomers if post-polymerization modification isdesirable to avoid.

The vinyl ether-maleimide copolymer adhesives are fully soluble andcastable in common/safe solvents (e.g., PGMEA). The ability of vinylether maleimide copolymer adhesives to be dissolved in a solvent, suchas propylene glycol monomethyl ether acetate (e.g., PGMEA), providesthat in wafer bonding techniques that employ laser debonding to detachthe temporarily attached wafers that the adhesive may easily be removedfrom the wafers by dissolving it in these solvents.

The above adhesive compositions described above as maleimide copolymercompositions are hereafter referred to as “high performance polymeradhesive” and/or “high performance polymer adhesives”. The highperformance polymer adhesives disclosed herein may be used in anylayer/substrate transfer and/or substrate bonding method used forforming semiconductor devices, memory devices, photovoltaic devices,microelectronic devices and nanoscale devices. For example, the highperformance polymer adhesives may be used in process that employmechanical spalling, such as the method described in U.S. Pat. No.8,247,261 titled “THIN SUBSTRATE FABRICATION USING STRESS INDUCEDSUBSTRATE SPALLING”. The high performance polymer adhesives may also beused as a bonding adhesives in methods for forming III-V semiconductorcontaining semiconductor devices and photovoltaic devices that include areusable germanium (Ge) containing substrate as a growth surface. Inthis example, once the III-V device is formed it is bonded to asupporting substrate, and the reusable germanium (Ge) containingsubstrate is removed from the III-V device to be used as the growthsurface for forming another device. The high performance polymeradhesives may also be used in layer transfer processes that employ smartcut to separate a portion of a material layer for transfer to asupporting substrate. Smart cut may include implanting a dopant species,such as hydrogen, into a material layer to provide a weakened interfaceacross when the material layer is to be cleaved. A portion of thecleaved material layer may be adhesively bonded to a supportingsubstrate using the high performance polymer adhesive. In otherembodiments, the high performance polymer adhesives may be employed in asubstrate, i.e., device wafer, thinning process. It is noted that theabove examples of adhesive applications for the high performance polymeradhesives is provided for illustrative purposes only, and is notintended to limit the present disclosure. Further details of the methodsand structures of the present disclosure that employ a high performancepolymer adhesives as a bonding adhesive as part of a method sequence forforming semiconductor devices that includes wafer thinning and debondingof a handling wafer are now discussed with greater detail with referenceto FIGS. 1-6.

FIG. 1 depicts one embodiment of a device wafer 5, e.g., semiconductorsubstrate, that may be employed in at least one embodiment of thepresent disclosure. In some embodiments, the device wafer 5 may beprovided by a bulk semiconductor substrate. The bulk semiconductorsubstrate may have a single crystal, i.e., monocrystalline, crystalstructure. In some embodiments, the device wafer 5 is composed of asilicon including material. In some embodiments, the silicon includingmaterial that provides the device wafer 5 may include, but is notlimited to silicon, single crystal silicon, multicrystalline silicon,polycrystalline silicon, amorphous silicon, strained silicon, silicondoped with carbon (Si:C), silicon alloys or any combination thereof. Inother embodiments, the device wafer 5 may be a semiconducting materialthat may include, but is not limited to, germanium (Ge), silicongermanium (SiGe), silicon germanium doped with carbon (SiGe:C),germanium alloys, GaAs, InAs, InP as well as other III/V and II/VIcompound semiconductors. The thickness T1 of the device wafer 5 mayrange from 10 microns to a few millimeters.

FIG. 2 depicts forming semiconductor devices 10 on a front surface 15 ofthe device wafer 5. As used herein, “semiconductor device” refers to anintrinsic semiconductor material that has been doped, that is, intowhich a doping agent has been introduced, giving it different electricalproperties than the intrinsic semiconductor. In some embodiments, thesemiconductor devices 10 are field effect transistors (FETs). A fieldeffect transistor (FET) is a transistor in which output current, i.e.,source-drain current, is controlled by the voltage applied to the gate.A field effect transistor typically has three terminals, i.e., gate,source and drain. The semiconductor devices 10 that may be formed usingthe methods of the present disclosure are applied to may be planarsemiconductor devices, FinFETS, Trigate semiconductor devices, nanowiresemiconductor devices or a combination thereof. The semiconductordevices 10 disclosed herein may also be provided by memory devices,e.g., flash memory or eDRAM memory.

In some embodiments, the semiconductor devices 10 may include a gatestructure 11 that includes at least one gate dielectric 12, at least onegate conductor 13 and at least one gate sidewall spacer 14.

The at least one gate dielectric 12 may be a dielectric material, suchas SiO₂, or alternatively high-k dielectrics, such as oxides of Ta, Zr,Al or combinations thereof. In another embodiment, the at least one gatedielectric 12 is comprised of an oxide, such as SiO₂, ZrO₂, Ta₂O₅ orAl₂O₃. In one embodiment, the at least one gate dielectric 12 may have athickness ranging from 1 nm to 10 nm.

The at least one gate conductor layer 13 may include a metal gateelectrode. The metal gate electrode may be any conductive metalincluding, but not limited to W, Ni, Ti, Mo, Ta, Cu, Pt, Ag, Au, Ru, Ir,Rh, and Re, and alloys that include at least one of the aforementionedconductive elemental metals. In other embodiments, the at least one gateconductor 13 may include a doped semiconductor material, such as a dopedsilicon containing material, e.g., doped polysilicon.

In some embodiments, a gate dielectric (not shown) may be present atopthe at least one gate conductor 13. The at least one gate dielectric capmay be composed of an oxide or nitride material.

Each of the material layers for the gate dielectric cap, the at leastone gate conductor layer 13, and the gate dielectric layer 12 may beformed using a deposition or growth process. For example, the gatedielectric layer 12 and the gate dielectric cap may be formed using achemical vapor deposition (CVD) process, such as plasma enhanced CVD(PECVD). The gate conductor layer 13 may be formed using a physicalvapor deposition (PVD) process, e.g., sputtering, when the gateconductor layer 13 is composed of a metal, or the gate conductor layer13 may be formed using a chemical vapor deposition (CVD) process whenthe gate conductor layer 3 is composed of a doped semiconductormaterial, e.g., polysilicon.

Following formation of the gate stack, the stack of material layers arepatterned and etched. Specifically, a pattern is produced by applying aphotoresist to the surface of the gate stack to be etched, exposing thephotoresist to a pattern of radiation, and then developing the patterninto the photoresist utilizing a resist developer. Once the patterningof the photoresist is completed, the sections covered by the photoresistare protected while the exposed regions are removed using a selectiveetching process that removes the unprotected regions. The etch processfor removing the exposed portions of the gate stack may be ananisotropic etch. As used herein, an “anisotropic etch process” denotesa material removal process in which the etch rate in the directionnormal to the surface to be etched is greater than in the directionparallel to the surface to be etched.

The anisotropic etch process may be provided by reactive ion etch.Reactive Ion Etching (RIE) is a form of plasma etching in which duringetching the surface to be etched is placed on the RF powered electrode.Moreover, during RIE the surface to be etched takes on a potential thataccelerates the etching species extracted from plasma toward thesurface, in which the chemical etching reaction is taking place in thedirection normal to the surface.

A gate sidewall spacer 14 can be formed in direct contact with thesidewalls of the gate stack. The gate sidewall spacers 14 are typicallynarrow having a width ranging from 2.0 nm to 15.0 nm. The gate sidewallspacer 14 can be formed using deposition and etch processing steps. Thegate sidewall spacer 14 may be composed of a dielectric, such asnitride, oxide, oxynitride, or a combination thereof.

FIG. 2 also depicts one embodiment of forming source and drain regions16, 17 on the opposing sides of the gate structure 11. As used herein,the term “drain” means a doped region in a semiconductor substrate thatis located at the end of the channel in field effect transistors (FET),in which carriers are flowing out of the transistor through the drain.As used herein, the term “source” is a doped region from which majoritycarriers are flowing into the channel. The source and drain regions 16,17 may be formed by ion implanting an n-type or p-type dopant into thedevice wafer 5. As used herein, “p-type” refers to the addition ofimpurities to an intrinsic semiconductor that creates deficiencies ofvalence electrons. In a type IV semiconductor, such as silicon (Si),examples of n-type dopants, i.e., impurities, include but are notlimited to: boron, aluminum, gallium and indium. As used herein,“n-type” refers to the addition of impurities that contributes freeelectrons to an intrinsic semiconductor. In a type IV semiconductor,such as silicon (Si), examples of n-type dopants, i.e., impurities,include but are not limited to antimony, arsenic and phosphorous.Typically, the conductivity type, i.e., n-type or p-type conductivity,for the source and drain regions 16, 17 is the conductivity type of thesemiconductor device, e.g., n-type field effect transistor (nFET) orp-type field effect transistor (pFET).

In some embodiments, multiple semiconductor devices 10 are formed on thefront side surface 15 of the device wafer 5, wherein the multiplesemiconductor devices 10 may include a first set of first conductivitytype semiconductor, e.g., n-type FET, and a second set a secondconductivity type, e.g., p-type FET. Isolation regions 18, such astrench isolation regions may be formed separating semiconductor devicesof different conductivity types, e.g., electrically isolated p-type FETSfrom n-type FETS. For example, lithography, etching and filling of thetrench with a trench dielectric may be used in forming the trenchisolation region. The trench isolation region may be composed of anoxide, such as silicon oxide.

FIG. 3 depicts bonding a handling wafer 25 to the front side surface 15of the device wafer 5 through an adhesive layer 20 containing the highperformance polymer adhesive. The adhesive layer 20 may be composed ofany of the high performance polymer adhesives that have been describedabove.

FIG. 3 depicts the device wafer 5 is bonded onto the handling wafer 25creating a compound wafer. The bonding process should be compatible withthe properties of the device wafer 5, such as surface topography,surface material, restrictions in process temperature, and combinationsthereof. In some examples, the temporary adhesive, i.e., adhesive layer20 containing high performance polymer adhesives, provides a planarsurface to the topography of the device wafer 5, and establishes a voidfree bond interface for bonding to the handling wafer 25.

The adhesion layer 20 may be applied to the front side surface 15 of thedevice wafer 5 covering the semiconductor devices 10 using a depositionprocess, such as spin coating. Typical spin solvents that are suitablefor depositing the adhesion layer 20 using spin coating may includePropylene Glycol Methyl Ether (PGME), Propylene glycol monomethyl etheracetate (PGMEA), ethyl lactate, N-Methyl-2-pyrrolidone (NMP) andcombinations thereof. In some embodiments, the spin coating solution mayfurther include cyclohexanone.

One example of a spin coating apparatus for depositing the adhesivelayer 20 is a fully automated coater system ACS200 from SUSS MicroTec.In one example, a center dispense of the liquid material may be employedfollowed by a spread spin at 1000 rpm for 10 seconds. After the spreadspin, the material was spun off at 1400 rpm for 60 seconds. It is notedthat the above described coating process is only one example of a methodof depositing the adhesion layer 20 on the front surface of the devicewafer 5, and that other deposition methods may be suitable for applyingthe adhesion layer 20 of high performance polymer adhesives. Forexample, the adhesion layer 20 may be deposited using spraying,brushing, curtain coating and dip coating.

Following application of the adhesive layer 20 of high performancepolymer adhesives to the front side surface 15 of the device wafer 5, ahandling wafer 25 is contacted to the surface of the adhesive layer 20that is opposite the surface of the adhesive layer 20 under temperatureand pressure to provide that the handling wafer 25 is bonded to thedevice wafer 5 through the adhesive layer 20. In some embodiments, thethickness T2 of the adhesive layer 20 between the handling wafer 25 andthe device wafer 5 may range from 2 microns to 10 microns. In otherembodiments, the thickness T2 of the adhesive layer 20 may range from 2microns to 5 microns.

The handling wafer 25 may be composed of a material and thickness tostructurally support the device wafer 5 without warping or crackingduring subsequent thinning steps, such as planarization and/or grinding.In one embodiment, the handling wafer 25 is composed of glass. In someembodiments, the material of the handling wafer is selected to have acoefficient of thermal expansion (CTE) that is similar to the CTE of thedevice wafer 5 to avoid any disadvantageous mechanical effects that canresult from two materials engaged to one another having differentthermal expansion coefficients, such as warping. In some embodiments, aglass handling wafer 25 may be advantageous to provide for transmissionof the laser signal through the glass handling wafer 25 duringsubsequent laser debonding steps. In other embodiments, the handlingwafer 25 may be composed of a metal material or a dielectric material.In some embodiments, the glass handling wafer 25 can be composed of asemiconductor material. For example, the above examples of semiconductormaterials for the device wafer 25 are equally suitable for thesemiconductor materials for the handling wafer 25.

To provide bonding, temperature and pressure was applied to thecomposite of the handling wafer 25, the adhesion layer 20 and the devicewafer. In one embodiment, the bonding temperature may range between 150°C. to 250° C., and the pressure applied may range from 0.07 MPA to 0.22MPa. In another embodiment, the bonding temperature may range from 150°C. to 200° C., and the pressure may range from 0.15 MPa to 0.22 MPa. Thetime period at which the bonding temperature and pressure is held mayrange from 10 minutes to 60 minutes. The bonding step may be performedin a nitrogen atmosphere. The above described bonding temperatures maybe modified to account for the different glass transition (Tg)temperatures that have been described above for the high performancepolymer adhesives.

Typically, bonding includes elevating the temperature of the adhesionlayer 20 of the high performance polymer adhesives to effectuate curingof the polymer. In some embodiments, an adhesive layer 20 composed ofthe high performance polymer adhesives has a viscosity ranging from100-10,000 Pa. seconds when at a temperature ranging from 160° C. to210° C., and under a pressure of 1000 mbar per area of an 8 inch wafersize for at least one of the device wafer 5 and/or handing wafer 20. Inanother embodiment, the viscosity of the high performance polymeradhesives at temperatures ranging from 160° C. to 210° C. may range from2500-10,000 Pa. second. In yet another embodiment, the viscosity of thehigh performance polymer adhesives at temperatures ranging from 160° C.to 210° C. may range from 5000-10,000 Pa. second. In one examples, theviscosity of the high performance polymer adhesives at temperaturesranging from 160° C. to 210° C. may be equal to 100, 200, 300, 400, 500,600, 700, 800, 900, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500,5000, 5500, 6000, 6500, 7000, 7500, 8000, 8500, 9000, 9500, and 10000Pa. second, and any range including at least two of the above notedvalues.

The adhesion layer 20 of high performance polymer adhesive followingbonding to the handling wafer 25 and the device substrate 5 may have ashear strength of 40 MPa or greater.

Another advantage of the present methods is that the curing of the highperformance polymer adhesives is at temperatures less than the curingtemperatures that are required of prior adhesives, such as polyimides.For example, imidization of polyimides requires temperatures greaterthan 300° C., which results in damage to the device wafer, such a waferwarpage and/or cracking. Additionally, the high temperatures required ofprior adhesives composed of polyimides may also result in unnecessaryout diffusion of the dopants of the semiconductor devices that have beenintegrated into the device wafer 5. Bonding with the high performancepolymer adhesives can be at temperatures below 300° C., which is at atemperature that does not damage, i.e., does not cause warping orcracking of the device wafer 5, and does not cause outdiffusion of thesemiconductor device dopants. In one embodiment, the bonding temperatureof the high performance polymer adhesives may range from 150° C. to 290°C. In another embodiment, the bonding temperature of the highperformance polymer adhesive may range from 160° C. to 210° C. In otherexamples, the bonding temperature of the high performance polymeradhesives may be at 150, 160, 170, 180, 190, 200, 210, 220, 240, 250,260, 270, 280 and 290° C., as well as any range including two of theaforementioned values.

In some embodiments, the high performance polymer adhesives that providethe adhesion layer 20 is not susceptible to degradation by exposure tothe following solvents: acetone, NMP, 6N HCl, 15% H₂O₂, 30% NH₄OH, 10%Kl in H₂O, EtOH, MeOH, Isopropyl Alcohol (IPA), cyclohexanone, ethyllactate, PGMEA, PGME, 30% HCl, 70% HNO₃ and combinations thereof.

FIG. 4 depicts thinning the backside surface 26 of the device wafer 5.The device wafer 5 may be thinned by applying a planarization processand/or a grinding process to the backside surface 26 of the device wafer5. In one example, the planarization and grinding process may beprovided by chemical mechanical planarization (CMP). In an alternativeembodiment, etch processes may be used to remove material from the backsurface 26 of the device wafer 5. Following thinning of the backsidesurface 26 of the device wafer 5, the thinned device wafer 5 may have athickness T3 ranging from 5 microns to 100 microns. In anotherembodiment, the thinned device wafer 5 may have a thickness T3 rangingfrom 20 microns to 50 microns. In one example, the thinned device wafer5 may have a thickness T3 ranging from 5 microns to 10 microns. Thehandling wafer 25 supports the device wafer 5 during the mechanicalthinning process to protect the device wafer 5 from mechanical failure,such as cracking.

FIG. 5 depicting one example of patterning the backside surface 26 ofthe thinned device wafer 5. The patterning step depicted in FIG. 5 maybe employed to form interconnects to the semiconductor devices 10 thatare integrated within the device wafer 5. For example, via interconnects30, such as through silica vias (TSV), may be formed to the activeregions of the device wafer 5. Through silica vias (TSV) may be employedto interconnect stacked devices wafers in forming a three dimensional(3D) microelectronic device. Vias can be formed to the active portionsof the semiconductor devices, e.g., source and drain regions 16, 17,using photoresist deposition, lithographic patterning to form aphotoresist etch mask, and etching, e.g., anisotropic etching. Followingvia formation, via interconnects 30 are formed by depositing aconductive metal into the via holes using deposition methods, such asCVD, sputtering or plating. The conductive metal may include, but is notlimited to: tungsten, copper, aluminum, silver, gold and alloys thereof.

FIG. 6 depicts one embodiment of debonding the handling wafer 25 fromthe device wafer 5. In one embodiment, debonding of the handling wafer25 may include laser debonding to ablate the adhesion layer 20containing the high performance polymer adhesives, and to remove thehandling wafer 25 from the device wafer 5. Laser debonding may beprovided by a 200 nm or 308 nm excimer laser. The UV laser may functionusing a cold process. For example, a 308 nm ultraviolet light emitted bythe excimer laser is absorbed near the interface between the devicewafer 5 and the glass handling wafer 25, penetrating only a few hundrednanometers. Thus, leaving the device wafer 5 unaffected. Furthermore,the ultraviolet light from the excimer laser debonds through primarily aphotochemical means, by directly breaking chemical bonds in the adhesionlayer 20 of high performance polymer adhesive. The excimer laser may beapplied in line mode, or step and repeat mode. The non-thermal processbreaks down the temporary adhesive, i.e., high performance polymeradhesive, at the adhesion layer 20 and glass handling wafer 25interface. Following application of the excimer layer, the handlingwafer 25 may be lifted and carried away from the device wafer 5.

In some embodiments, high performance polymer adhesive that remains onthe device wafer 5 and/or carrier wafer 25 following removal of theadhesion layer 20 may be removed using a solvent, such as propyleneglycol monomethyl ether acetate (e.g., PGMEA). In other embodiments, thesolvent that is used for removing the high performance polymer adhesivemay be selected from the group consisting of gamma-butyrolactone, ethyllactate, other lactate isomers known under the tradename Gavesolv, NMP,Tetrahydrofuran (THF), PMAcetate, Methyl isobutyl ketone (MIBK), Methylethyl ketone (MEK), and combinations thereof.

FIG. 7 is a flow chart illustrating an approach for performing handlersubstrate bonding and de-bonding in accordance with another exemplaryembodiments of the present disclosure. Referring to FIGS. 7 and 8, theadhesive layer 230 may be applied to at least one of the semiconductorcontaining handler substrate 210 and the semiconductor containing devicesubstrate 220 at step 100. The adhesive layer 230 is typically composedof a high performance polymer adhesive, as described above for theadhesive layer 20 that is depicted in FIGS. 3-5. Therefore, thedescription of the adhesive layer 20 that is depicted in FIGS. 3-5 canprovide the description of some embodiments of the adhesive layer 230that is depicted in FIG. 8. For example, the adhesive layer 230 may beany of the above described maleimide copolymers or terpolymers, whichcan include styrene maleimide copolymer, styrene/phenyl maleimidecopolymer, vinyl ether-maleimide copolymer and combinations thereof.

In one embodiment, an adhesive layer 230 may be applied to one of thesemiconductor containing handler substrate 220, and the semiconductorcontaining device substrate 210, and a release layer 240 may be appliedto the other of the semiconductor containing handler substrate 210 andthe semiconductor containing device substrate 220. In this example, boththe adhesive layer 230 and the release layer 240 may be composed of thehigh performance maleimide copolymer or terpolymer adhesives describedabove, e.g., styrene maleimide copolymer, styrene/phenyl maleimidecopolymer, vinyl ether-maleimide copolymer and combinations thereof.

Referring to FIGS. 7 and 8, in some embodiments, the device substrate210 may be provided by a bulk semiconductor substrate. The devicesubstrate 210 is similar to the device wafer 5 described above withreference to FIG. 2. For example, the device substrate 210 may becomposed of crystalline silicon. The semiconductor containing devicesubstrate 210 may include at least one semiconductor device, which maybe planar semiconductor devices, FinFETS, Trigate semiconductor devices,nanowire semiconductor devices or a combination thereof. Thesemiconductor devices present in the semiconductor containing devicesubstrate 210 may also include memory devices, e.g., flash memory oreDRAM memory.

The handler substrate 220 may also be composed of a semiconductormaterial. In one example, the handler substrate 220 may be a glasssubstrate. It is noted that the handler substrate 220 that is depictedin FIG. 8 is similar to the handling wafer 25 that is depicted in FIG.3. Therefore, the description of the handling wafer 25 that is depictedin FIG. 3 is suitable for the handler substrate 220 that is depicted inFIG. 8.

As noted above, the adhesive layer 230 and the release layer 240 areapplied to at least one of the semiconductor containing device substrate210 and the semiconductor containing handler substrate 220. Althoughembodiments have been contemplated in which both the adhesive layer 230and the release layer 240 are composed of high performance polymeradhesives, such as the above maleimide copolymers or terpolymers, whichcan include styrene maleimide copolymer, styrene/phenyl maleimidecopolymer, vinyl ether-maleimide copolymer and combinations thereof, itis not necessary that each of the layers be composed of those materials.For example, in some other embodiments, the release layer 240 may becomposed of a polyimide-based adhesive, such as HD3007, which can bespin applied and cured at 350° C. In yet other embodiments, the releaselayer 240 may be composed of a thermoplastic resin, such as phenoxyresin, e.g., Phenoxy Resin PKHC®, PKHH® or PKHJ® available from InChemCorp. In one example, one of the adhesive layer 230 and/or release layer240 may be a phenoxy resin having the chemical name:polyoxy(2-hydrozy-1,3propanediyl)oxy-1,4-phenylene(1-methylethylidene)-1,4-phenylene.

Applying the adhesion layer 230 and/or the release layer 240 may beapplied to the front side surface of the semiconductor containing devicesubstrate 21 and the semiconductor containing handler substrate 22 usinga deposition process, such as spin coating. Typical spin solvents thatare suitable for depositing the adhesion layer 23 and/or the releaselayer 240 using spin coating may include Propylene Glycol Methyl Ether(PGME), Propylene glycol monomethyl ether acetate (PGMEA), ethyllactate, N-Methyl-2-pyrrolidone (NMP) and combinations thereof. In someembodiments, the spin coating solution may further includecyclohexanone. The release layer 240 may also be optional.

Spin coating parameters may depend on the viscosity of the adhesionlayer 230 and/or the release layer 240, but may fall in the range fromapproximately 500 rpm to approximately 3000 rpm. One example of a spincoating apparatus for depositing the adhesion layer 230 and/or therelease layer 240 is a fully automated coater system ACS200 from SUSSMicroTec. In one example, a center dispense of the liquid material maybe employed followed by a spread spin at 1000 rpm for 10 seconds. Afterthe spread spin, the material was spun off at 1400 rpm for 60 seconds.It is noted that the above described coating process is only one exampleof a method of depositing the adhesion layer 230 and/or the releaselayer 240 on either of the semiconductor containing device substrate 210or the semiconductor containing handler substrate 220, and that otherdeposition methods may be suitable for applying the adhesion layer 230and/or the release layer 240. For example, the adhesion layer 230 and/orthe release layer 240 may be deposited using spraying, brushing, curtaincoating and dip coating.

In some embodiments, following application of the adhesion layer 230and/or the release layer 240 by spin coating, and prior to the waferbonding step, the spin coated layer of material may be cured. Thesoft-bake may fall in the range from approximately 80° C. toapproximately 120° C. The temperature of the final cure may fall in therange from 200° C. to 400° C. Higher cure temperatures may be moreeffective at ensuring thermal stability of the UV ablation layer duringstandard CMOS BEOL processing which may take place between 350° C. and400° C.

Referring to FIG. 7, following application of the adhesive layer 230and/or the release layer 240, the semiconductor containing devicesubstrate 210 may be bonded to the semiconductor containing handlersubstrate 220 at step 110, such that the release layer 230 and theadhesive layer 240 are provided between the semiconductor containingdevice substrate 210 and the semiconductor containing handler substrate220. The bonding may include a physical bringing together of thesemiconductor containing device substrate 210 and the semiconductorcontaining handler substrate 220 under controlled heat and pressure in avacuum environment, such as offered in any one of a number of commercialbonding tools.

In some embodiments, to provide bonding, temperature and pressure mayapplied to the composite of the semiconductor containing handlersubstrate 220, the adhesion layer 230, the optional release layer 240,and the semiconductor containing device substrate 210. In oneembodiment, the bonding temperature may range between 150° C. to 250°C., and the pressure applied may range from 0.07 MPA to 0.22 MPa. Inanother embodiment, the bonding temperature may range from 175° C. to200° C., and the pressure may range from 0.15 MPa to 0.22 MPa. The timeperiod at which the bonding temperature and pressure is held may rangefrom 10 minutes to 60 minutes. The bonding step may be performed in anitrogen atmosphere. Each of the adhesive layer 240, and the releaselayer 230 (when present), following bonding to the semiconductorcontaining handler wafer 220, and the semiconductor containing devicesubstrate 210 may have a shear strength of 40 MPa or greater. It isnoted that further details regarding the bonding at step 210 of theprocess flow depicted in FIG. 7 is found in above with reference to thebonding steps depicted in FIG. 3.

Referring to FIG. 7, in some embodiments, after bonding to provide thecomposite of the semiconductor containing handler substrate 210, theadhesion layer 230, the optional release layer 240, and thesemiconductor containing handler substrate 220, the desired processingmay be performed to the backside surface of the semiconductor containingdevice substrate 210 at step 120. The backside surface of thesemiconductor containing device substrate 210 is not engaged to one ofthe adhesive layer 230 or the release layer 240. The backside surface ofthe semiconductor containing device substrate 210 is typically oppositethe surface of the semiconductor containing device substrate 210 thatthe semiconductor devices may be formed on, which may be referred to asthe upper surface of the semiconductor containing device substrate 210.For example, backside processing may include such process steps aspatterning, etching, thinning, etc. until the device wafer has achievedits desired state.

For example, in one embodiment, the semiconductor containing devicesubstrate 210 may be thinned by applying a planarization process and/ora grinding process to the backside surface of the semiconductorcontaining device substrate 210. In one example, the planarization andgrinding process may be provided by chemical mechanical planarization(CMP). In an alternative embodiment, etch processes may be used toremove material from the back surface of the semiconductor containingdevice substrate 210. Following thinning of the backside surface of thesemiconductor containing device substrate 210, the thinned semiconductorcontaining device substrate 210 may have a thickness ranging from 5microns to 100 microns. In another embodiment, the thinned semiconductorcontaining device substrate 210 may have a thickness ranging from 20microns to 50 microns. In one example, the thinned semiconductorcontaining device substrate 210 may have a thickness ranging from 5microns to 10 microns. The semiconductor containing handler substrate220 supports the semiconductor containing device substrate 210 duringthe mechanical thinning process to protect the semiconductor containingdevice substrate 210 from mechanical failure, such as cracking.

In another example, the backside processing of the semiconductorcontaining device substrate 210 may include a patterning step to forminterconnects to the semiconductor devices that are integrated withinthe semiconductor containing device substrate 210. Further detailsregarding forming the interconnects have been provided above withreference to FIG. 5.

After backside processing of the semiconductor containing devicesubstrate 210, a laser ablation process may be performed to sever thesemiconductor containing device substrate 210 from the semiconductorcontaining handler substrate 220 at step 130. During the laser ablationprocess, a laser emits a wavelength of light that is absorbed by atleast one of the release layer 240 (when present), and the adhesivelayer 230. To be transmitted through the semiconductor containinghandler substrate 220, e.g., silicon (Si) handler substrate, and/or thesemiconductor containing device substrate 210 to expose at least one ofthe adhesive layer 230 and a release layer 240 to the wavelengths oflight being emitted from the laser at the bonded interface of thesemiconductor containing device substrate 210 and the semiconductorcontaining handler substrate 220, the wavelength of light being emittedfrom the laser should be within the infra-red (IR) range or ultraviolet(UV) range. Upon exposure to the infra-red (IR) laser light, at leastone of the adhesive layer 230 and the release layer 240 may burn, breakdown, or otherwise decompose. In yet other embodiments, the absorptionof the infra-red (IR) or ultra-violet (UV) wavelengths by at least oneof the adhesive layer 230 and the release layer 240 may cause the layerabsorbing the infra-red (IR) wavelengths to melt. The burning, breakdown, melting or otherwise decomposition of at least one the adhesivelayer 230 and the release layer 240 is referred to as “ablating” of thematerial layer with the infra-red (IR) laser.

Laser debonding to sever the semiconductor containing device substrate210 from the semiconductor containing handler substrate 220 at step 130may be performed using any one of a number of UV laser sources includingexcimer lasers operating at 308 nm (e.g. XeCl) or 351 nm (e.g. XeF) aswell as diode-pumped (tripled) YAG laser operating at 355 nm ordiode-pumped (quadrupled) YAG laser operating at 266 nm. UV ablationthresholds in the materials specified here may require 100-150milliJoules per square cm (mJ/sq·cm) to effect release. Another laserdebonding system may include a solid-state pumped tripled YAG laser at355 nm by rapidly scanning a small spot beam across the wafer surface.

An exemplary 355 nm scanning laser debonding system may include aQ-switched tripled YAG laser with an output power of 5 to 10 Watts at355 nm, with a repetition rate between 50 and 100 kHz, and pulse widthof between 10 and 20 ns. In one embodiments, infra-red (IR) lightsuitable for use with the present disclosure includes light with awavelength ranging at a lower limit of the range from ≈700 nm to 800 nm,to a wavelength at an upper limit range, which may be 1 mm. Any laseremitting light within these wavelengths can be referred to as infra-red(IR) laser, and are suitable for ablating at least one of the adhesivelayer 230, and the release layer 240, that is present at the bondedinterface between the semiconductor containing device substrate 210, andthe semiconductor containing handler substrate 220. For example, somelaser diodes can emit wavelengths beyond 750 nm. In some embodiments,lasers suitable for laser ablating in accordance with present disclosureinclude lasers that emit light waves in the near-infrared spectralregion (also called IR-A), which may range from ≈700 nm to 1400 nm. Inother embodiments, the infra-red (IR) laser for ablating the releaselayer 240 and the adhesive layer 230 may emit short-wavelength infrared(SWIR, IR-B), which includes light waves extending from 1.4 to 3 μm. Inyet other embodiments, the IR laser for ablating the release layer 240and the adhesive layer 230 may emit mid-infrared (mid-wavelengthinfrared, MWIR, IR-C), which include wavelengths of light that may rangefrom 3 μm to 8 μm. In yet even further embodiments, the IR laser forablating the release layer 240 and the adhesive layer 230 may includelong-wavelength infrared (LWIR, IR-C) ranges from 8 to 15 μm. In someembodiments, the IR laser for ablating the release layer 240, and theadhesive layer 230, may include long-wavelength infrared (LWIR, IR-C)followed by the far infrared (FIR), which ranges to 1 mm and issometimes understood to start at 8 μm.

In some embodiments, the laser for ablating at least one of the releaselayer 240 and the adhesion layer 230 includes Nd:YAG (neodymium-dopedyttrium aluminum garnet; Nd:Y₃Al₅O₁₂) lasers, helium neon (HeNe) lasers,krypton laser, carbon dioxide (CO₂) laser, carbon monoxide (CO) laser ora combination thereof.

Nd:YAG lasers are optically pumped using a flashtube or laser diodes.Nd:YAG lasers typically emit light with a wavelength of 1064 nm, in theinfra-red (IR). However, there are also transitions near 940 nm, 1120nm, 1320 nm, and 1440 nm. Nd:YAG lasers operate in both pulsed andcontinuous mode. Pulsed Nd:YAG lasers are typically operated in theso-called Q-switching mode. In this Q-switched mode, output powers of250 megawatts, and pulse durations of 10 to 25 nanoseconds have beenachieved. Nd:YAG absorbs mostly in the bands between 730-760 nm and790-820 nm. The amount of the neodymium dopant in the material variesaccording to its use. For continuous wave output, the doping issignificantly lower than for pulsed lasers. Some common host materialsfor neodymium are: YLF (yttrium lithium fluoride, 1047 and 1053 nm),YVO₄ (yttrium orthovanadate, 1064 nm), and glass. Nd:YAG lasers andvariants are pumped either by flashtubes, continuous gas dischargelamps, or near-infrared laser diodes (DPSS lasers).

Helium-neon lasers may emit a wavelength of light ranging fromapproximately 1.15 μm to approximately 3.4 μm. A helium-neon laser orHeNe laser, is a type of gas laser whose gain medium consists of amixture of helium and neon (10:1) inside of a small bore capillary tube,usually excited by a DC electrical discharge.

A krypton laser may emit a wavelength of light ranging on the order of750 nm. A krypton laser is an ion laser, a type of gas laser usingkrypton ions as a gain medium, pumped by electric discharge.

Carbon dioxide (CO₂) lasers can emit light wavelengths at 10.6 μm, andsome other wavelengths in that region, e.g., micrometer wavelengthsbeing greater than 9.5 μm. Carbon dioxide (CO₂) lasers are gas lasersthat are one of the highest-power continuous wave lasers, in which theratio of output power to pump power can be as large as 20%. The pumpsource for carbon dioxide (CO₂) lasers may be transverse (high power) orlongitudinal (low power) electrical discharge.

Carbon monoxide (CO) lasers can emit light wavelengths that in someembodiments can range from 2.6 μm to 4 μm, and in some other embodimentscan range from 4.8 μm to 8.3 μm. The pump source for carbon monoxide(CO) lasers may be electrical discharge.

The at least one of the release layer 240 and the adhesive layer 230according to exemplary embodiments of the present disclosure comprises amaterial that is broken down under the exposure of the infra-red (IR) orultraviolet (UV) laser light. Where desired, the remainder of theadhesive layer 230 or release layer 240 that is not ablated by theinfra-red (IR) or ultraviolet (UV) laser may be removed from either ofthe semiconductor containing device substrate 210 and the semiconductorcontaining handler substrate 220 using various processing techniques.

Referring to FIG. 7, after the laser ablation has resulted in thesevering of the semiconductor containing device substrate 210 from thesemiconductor containing handler substrate 220, the semiconductorcontaining device substrate 210 may be easily removed from thesemiconductor containing handler substrate 220, e.g., by simply pullingthe semiconductor containing handler substrate 220 away, and thesemiconductor containing device substrate 210 may be cleaned to removethe adhesive layer 230, or remaining portion of the adhesive layer 230at step 140.

In some embodiments, residues of adhesive layer 230 or release layer240, e.g., residues from the high performance maleimide copolymer orterpolymer adhesives, that remains on one of the semiconductorcontaining handler substrate 220, and the semiconductor containingdevice substrate 210, following removal of the release layer 240 may beaccomplished using a solvent selected from the group consisting ofgamma-butyrolactone, ethyl lactate, other lactate isomers known underthe tradename Gavesolv, NMP, Tetrahydrofuran (THF), PMAcetate, Methylisobutyl ketone (MIBK), Methyl ethyl ketone (MEK), gamma-butyrolactone,ethyl lactate, other lactate isomers known under the tradename Gavesolv,NMP, Tetrahydrofuran (THF), PMAcetate, Methyl isobutyl ketone (MIBK),Methyl ethyl ketone (MEK), and combinations thereof.

FIGS. 9A and 9B are schematic diagrams illustrating pattern of applyingthe laser light to a top surface 310 of the semiconductor containinghandler substrate 220 in accordance with exemplary embodiments of thepresent disclosure. As seen in FIG. 9A, the laser light may be directedacross the top surface 310 of the semiconductor containing handlersubstrate 220 as a spot beam drawn to lines 320 which move along anx-axis direction of the top surface 310 of the semiconductor containinghandler substrate 220 with each successive line 320 being drawn lower inthe y-axis direction. Alternatively, as seen in FIG. 9B, the laser lightmay be directed in a serpentine pattern 330.

FIG. 10 is a schematic diagram illustrating an apparatus for performinglaser de-bonding in accordance with exemplary embodiments of the presentdisclosure. According to some exemplary embodiments of the presentdisclosure, such as is shown here in FIG. 10, the bonded semiconductorcontaining handler substrate and semiconductor containing devicesubstrate 410 may remain stationary, e.g., on a stage. According toother exemplary embodiments, the stage may be movable. The laser 420,i.e., IR or UV laser, may provide a beam that may then be sent into abeam expander 450 to provide the desired beam size. The beam may thenenter a scanner 460 where the beam can be directed along the x and yaxes. One or more control units 430 may affect control of the laser 420,beam expander 450 and the scanner 460. Where the stage upon which thebonded handler and wafer 410 are held is movable, the controller 430 maycontrol the movement of the stage as well. In such a case the scanner460 may be omitted. A computer system 440 may be preprogrammed with themanner of control and these instructions may be executed though the oneor more control units 430. A scan lens 470 may adjust the beam so as tostrike the bonded handler and device wafer 410 with the desired spotcharacteristics.

Methods as described herein may be used in the fabrication of integratedcircuit chips. The resulting integrated circuit chips can be distributedby the fabricator in raw wafer form (that is, as a single wafer that hasmultiple unpackaged chips), as a bare die, or in a packaged form. In thelatter case the chip is mounted in a single chip package (such as aplastic carrier, with leads that are affixed to a motherboard or otherhigher level carrier) or in a multichip package (such as a ceramiccarrier that has either or both surface interconnections or buriedinterconnections). In any case the chip is then integrated with otherchips, discrete circuit elements, and/or other signal processing devicesas part of either (a) an intermediate product, such as a motherboard, or(b) an end product. The end product can be any product that includesintegrated circuit chips, ranging from toys and other low-endapplications to advanced computer products having a display, a keyboardor other input device, and a central processor.

EXAMPLES

The following examples are intended to provide those of ordinary skillin the art with a complete disclosure and description of how to prepareand use the compositions disclosed and claimed herein. Efforts have beenmade to ensure accuracy with respect to numbers (e.g., amounts,temperature, etc.), but allowance should be made for the possibility oferrors and deviations.

Data Set 1

A description follows for 10 polymer compositions (identified as polymer1, polymer 2, polymer 3, polymer 4, polymer 5, polymer 6, polymer 7,polymer 8, polymer 9 and polymer 10) and chemical structures that aresuitable for use with the methods, structures and adhesive compositionsdescribed above. The experimental procedures for synthesizing thepolymer compositions is also provide. A following section providescharacterization of the six polymer compositions, which includesmolecular weight Mw, polydispersity index (PDI), number averagemolecular weight Mn, thermal stability, and glass transition temperature(Tg).

Polymer Compositions and Chemical Structure

Polymer 1 Poly(Styrene-co-N-phenylmaleimide-co-maleic anhydride),x:y:z=2.00:0.76:0.24)

Polymer 2 Poly(Styrene-co-N-phenylmaleimide-co-maleic anhydride),x:y:z=1.30:0.84:0.16

Polymer 3 Poly(Styrene-co-N-phenylmaleimide), x:y=0.48:0.52

Polymer 4 Poly(Norbornenene-co-N-phenylmaleimide), x:y=1:2

Polymer 5 Poly(Styrene-co-N-hexylmaleimide-co-maleic anhydride),x:y:z=2.0:0.80:0.20

Polymer 6 Poly(Methyl vinyl ether-co-N-butylmaleimide-co-maleicanhydride), x:y:z=1.00:0.85:0.15

Polymer 7 Poly(butyl vinyl ether-co-N-phenylmaleimide), x:y=40:60

Polymer 8 Poly(butyl vinyl ether-co-N-methylmaleimide), x:y=40:60

Polymer 9 Poly(butyl vinyl ether-co-N-ethylmaleimide) x:y=40:60

Polymer 10 Poly(dodecyl vinyl ether-co-phenylmaleimide) x:y=40:60

Polymer Synthesis of Polymers 1-10:

Polymer 1: Poly(styrene-co-maleic anhydride) 2:1, purchased from AldrichChemical Company, (20 grams, 0.065 moles of anhydride units) wasdissolved in 200 ml N,N-dimethyl formamide (DMF). Aniline (10 grams,0.108 mole) was added to this solution and heated to reflux for 5.5hours. After allowing it to cool to room temperature, the solution wasadded drop wise into a solution of 2 liters of deionized water and 60grams of concentrated HCl. The polymer was filtered through a fritfunnel, washed with 250 ml deionized (DI) water and suction dried for 4hours. This polymer was then dissolved in 250 ml acetone andprecipitated again into a solution of 3 liters of water and 90 grams ofconcentrated HCl. This polymer was filtered, washed with 250 ml DI waterand dried under vacuum at 90° C. for 24 hours. Yield was 23.64 grams.

Polymer 2: Poly(styrene-co-maleic anhydride) 1.3:1, purchased fromAldrich Chemical Company, (20 grams, 0.086 moles of anhydride units) wasdissolved in 200 ml N,N-dimethyl formamide (DMF). Aniline (12 grams,0.128 mole) was added to this solution and heated to reflux for 5 hours.After allowing it to cool to room temperature, the solution was addeddrop wise into a solution of 2 liters of deionized water and 60 grams ofconcentrated HCl. The polymer was filtered through a frit funnel, washedwith 250 ml DI water and suction dried for 4 hours. This polymer wasthen dissolved in 135 ml acetone and precipitated again into a solutionof 1.3 liters of water and 30 grams of concentrated HCl. This polymerwas filtered, washed with 250 ml DI water and dried under vacuum at 90°C. for 24 hours. Yield was 25.04 grams.

Polymer 3: Styrene (7.81 g, 0.075 mole) and N-phenylmaleimide (13.00 g,0.075 mole) and 187.29 grams of DMF were placed in a round bottom flaskequipped with a condenser and a nitrogen inlet.2,2′-Azobisisobutyronitrile (AIBN), (0.99 g, 0.006 mole) was added tothis solution and stirred until dissolved. Then, the solution wasdegassed using four vacuum/nitrogen purges. The contents were thenheated at 90° C. for 18 hours.

Afterwards, the solution was added drop wise into a solution of 2 litersof DI water and 60 grams of concentrated HCl. The precipitated polymerwas filtered (frit), washed twice with water (250 ml) and dried undervacuum at 90° C. The polymer was then dissolved in 250 ml oftetrahydrofuran (THF), and precipitated again into a solution of 2liters of water and 60 grams of concentrated HCl. The polymer wasfiltered, washed with 250 ml DI water and dried under vacuum at 90° C.for 24 hours. Yield was 20.65 grams.

Polymer 4: Norbornene (9.42 g, 0.10 mole) and N-phenylmaleimide (17.32g, 0.010 mole) and 240 grams of DMF were placed in a round bottom flaskequipped with a condenser and a nitrogen inlet.2,2′-Azobisisobutyronitrile (AIBN), (1.32 g, 0.008 mole) was added tothis solution and stirred until dissolved. Then, the solution wasdegassed using four vacuum/nitrogen purges. The contents were thenheated at 90° C. for 18 hours. Afterwards, the solution was added dropwise into a solution of 2.8 liters of DI water and 40 grams ofconcentrated HCl. The precipitated polymer was filtered (frit), washedtwice with water (250 ml) and dried under vacuum at 90° C. This polymerwas then dissolved in 150 ml of tetrahydrofuran (THF) and precipitatedagain into 3 liters of hexanes. This polymer was filtered, washed with150 ml hexanes and dried under vacuum at 90° C. for 18 hours. Yield was15.13 grams.

Polymer 5: Poly(styrene-co-maleic anhydride) 2:1, purchased from AldrichChemical Company, (20 grams, 0.065 moles of anhydride units) wasdissolved in 200 ml N,N-dimethyl formamide (DMF). Hexylamine (10.2grams, 0.10 mole) was added to this solution and heated to reflux for 18hours. After allowing it to cool to room temperature, the solution wasadded drop wise into a solution of 3 liters of deionized water and 80grams of concentrated HCl. The polymer was filtered through a fritfunnel, washed twice with 250 ml DI water and suction dried for 4 hours.This polymer was then dried under vacuum at 90° C. for 24 hours. Yieldwas 24.13 grams.

Polymer 6: Poly(methyl vinyl ether-alt-maleic anhydride), purchased fromAldrich Chemical Company, (46.8 grams, 0.30 moles of anhydride units)was dissolved in 400 ml N,N-dimethyl formamide (DMF). Butylamine (22.2grams, 0.303 mole) was added to this solution and heated to reflux for 7hours. After allowing it to cool to room temperature, the solution wasadded drop wise into a solution of 3.6 liters of deionized water and 45grams of concentrated HCl. The polymer was filtered through a fritfunnel, washed twice with 300 ml DI water and suction dried for 18hours. This polymer was then dried under vacuum at 90° C. for 72 hours.Yield was 47.32 grams.

Polymer 7: N-butyl vinyl ether (5.71 g, 0.057 mole) andN-phenylmaleimide (9.86 g, 0.075 mole) and 140.13 grams of DMF wereplaced in a round bottom flask equipped with a condenser and a nitrogeninlet. 2,2′-Azobisisobutyronitrile (AIBN), (0.75 g, 0.0045 mole) wasadded to this solution and stirred until dissolved. Then, the solutionwas degassed using four vacuum/nitrogen purges. The contents were thenheated at 80° C. for 18 hours. Afterwards, the solution was added dropwise into a solution of 1.5 liters of DI water and 35 ml of concentratedHCl. The precipitated polymer was filtered (frit), washed twice withwater (250 ml) and dried under vacuum at 95° C. for 30 hours. Yield:13.24 grams.

Polymer 8: N-butyl vinyl ether (5.6 g, 0.0557 mole) andN-methylmaleimide (6.19 g, 0.0557 mole) and 106.11 grams of DMF wereplaced in a round bottom flask equipped with a condenser and a nitrogeninlet. 2,2′-Azobisisobutyronitrile (AIBN), (0.73 g, 0.0044 mole) wasadded to this solution and stirred until dissolved. Then, the solutionwas degassed using four vacuum/nitrogen purges. The contents were thenheated at 90° C. for 18 hours. Afterwards, the solution was added dropwise into a solution of 1.5 liters of DI water and 35 ml of concentratedHCl. The precipitated polymer was filtered (frit), washed twice withwater (250 ml) and dried under vacuum at 95° C. for 20 hours. Yield:8.16 grams.

Polymer 9: N-butyl vinyl ether (5.68 g, 0.0567 mole) andN-ethylmaleimide (7.10 g, 0.0567 mole) and 115.02 grams of DMF wereplaced in a round bottom flask equipped with a condenser and a nitrogeninlet. 2,2′-Azobisisobutyronitrile (AIBN), (0.56 g, 0.0034 mole) wasadded to this solution and stirred until dissolved. Then, the solutionwas degassed using four vacuum/nitrogen purges. The contents were thenheated at 85° C. for 18 hours. Afterwards, the solution was added dropwise into a solution of 1.2 liters of DI water and 20 ml of concentratedHCl. The precipitated polymer was filtered (frit), washed twice withwater (300 ml) and dried under vacuum at 95° C. for 20 hours. Yield:9.65 grams.

Polymer 10: N-dodecyl vinyl ether (6.68 g, 0.0315 mole) andN-phenylmaleimide (5.45 g, 0.0315 mole) and 48.52 grams of DMF wereplaced in a round bottom flask equipped with a condenser and a nitrogeninlet. 2,2′-Azobisisobutyronitrile (AIBN), (0.052 g, 0.00031 mole) wasadded to this solution and stirred until dissolved. Then, the solutionwas degassed using four vacuum/nitrogen purges. The contents were thenheated at 80° C. for 18 hours. Afterwards, the solution was added dropwise into a solution of 800 ml of DI water and 15 ml of concentratedHCl. The precipitated polymer was filtered (frit), washed twice withwater (300 ml) and dried under vacuum at 80° C. for 72 hours. Yield:10.67 grams. This polymer according to NMR data had some monomer(dodecyl vinyl ether) left. 7 grams of this polymer was dissolved in 35ml acetone. This solution was slowly added into 700 ml of methanol. Theprecipitated polymer was filtered (frit) and dried under vacuum at 90°C. for 18 hours. Yield: 5.29 grams.

Characterization:

¹H and ¹³C NMR spectra for polymers 1-6 were obtained for poluat roomtemperature on an Avance 400 spectrometer. Quantitative ¹³C NMR was onpolymers 1-6 run at room temperature in acetone-d₆ in an inverse-gated¹H-decoupled mode using Cr(acac)₃ as a relaxation agent on an Avance 400spectrometer. Thermo-gravimetric analysis (TGA) was performed onpolymers 1-6 at a heating rate of 10° C./min in N₂ on a TA InstrumentHi-Res TGA 2950 Thermogravimetric Analyzer. Differential scanningcalorimetry (DSC) was performed on each of polymers 1-6 at a heatingrate of 4° C./min on a TA Instruments DSC 2920 modulated differentialscanning calorimeter. Molecular weights were measured in tetrahydrofuran(THF) or dimethylformamide (DMF) on a Waters Model 150 chromatographrelative to polystyrene standards. The results of the characterizationof the polymers is included in the following Table 1:

TABLE 1 CHARACTERIZATION OF POLYMER COMPOSITIONS 1-10 Thermal Stability° C. T_(g) ° C. Polymer M_(w) M_(n) PDI Wt. loss <5% (TGA) (DSC) 1 7,3534,238 1.73 300 160 2 6.231 3,545 1.76 300 180 3 55,187 22,565 2.44 300209 4 1,965 1,312 1.50 300 182 5 8,424 4,722 1.78 300 92 6 5,169 3,6941.40 300 90 7 13,824 6,617 2.08 300 160 8 13,569 6,734 2.01 300 142 915,744 7,694 2.04 300 119 10 33,614 19,048 1.76 300 107Data Set 2

Optimization of Polymer 10 (Poly(dodecyl vinyl ether-co-phenylmaleimide)

Poly(dodecyl vinyl ether-co-phenylmaleimide) was further optimized bychanging the solvent, percentage of the solids in the solution, amountof initiator (AIBN), and the temperature of the polymerization reaction.The conditions and the polymer properties are presented in Table 2,which describes Polymers 11-15 that are each based upon Poly(dodecylvinyl ether-co-phenylmaleimide).

TABLE 2 POLY(DODECYL VINYL ETHER-CO-PHENYLMALEIMIDE) REACTION CONDITIONSAND PROPERTIES: Comp By Poly Condition AIBN Temp NMR (x:y) Mn Mw TgYield 11 25 wt % in 0.5 mol % 70° C. 40:60 23,881 42,360 114C 70% DMF 1235 wt % in 0.5 mol % 70° C. 40:60 33,489 58,572 113C 70% DMF 13 35 wt %in 0.25 mol %  70° C. 40:60 29,238 51,576 111C 70% DMF 14 33 wt % in No60° C. 45:65 167,740 339,741 100C 25% CHCL3 Initiator 15 33% in 0.5 mol% 60° C. 45:55 76,244 188,510 101C 84% CHCL3Adhesive Materials Pre-Screen Protocol for Data Set 2

Test polymer for were dissolved in a spin solvent (e.g., PGMEA orCyclohexanone) to a solution of 30-40% solids. Solution was filteredwith 1 μm glass filter. Polymer solution was spun cast on a 1 inchsilicon wafer (or larger) at 1500 rpm, with a ramp speed of 100 rpm/sfor a total of 60 seconds. The polymer coated wafer was pre-baked at110° C. for 2 minutes and thereafter directly transferred to a 250° C.or 300 C hotplate (no chilling) and baked for 5 minutes. The baked waferwas removed from the hotplate and suspended in air for slow cooling orcooled on a chill plate. Observations of coating quality after spin,pre-bake, main bake and chill was noted. Thickness was measured by aprofilometer. Solubility of film was tested in cold and hot spinningsolvent (e.g., PGMEA), cold and hot EKC865™ and/or cold or hot NMP inorder as listed until film was dissolved. From the above notedpre-screen protocal, polymer compositions 11 and 12 were selected forfurther evaluation.

Evaluation of Polymers 11 and 12

A solution was made in propylene glycol monomethyl ether acetate (PGMEA)and the solution was filtered through a 1 micrometer glass filter. Thissolution was spun cast on a 4″ silicon wafer at 1500 rpm (ramp: 50rpm/s) and prebaked at 110° C. for 2 minutes. Then the film was baked at250° C. for 5 minutes and the dissolution properties were determined.The results are presented in Table 3.

TABLE 3 DISSOLUTION AND THICKNESS OF POLYMERS 11 AND 12 Thickness after250 C. Dissolution after 250 C. Formulation bake bake 35 wt % solutionof 7.4 micrometer Soluble within 10 minutes polymer 11 in PGMEA andEKC865 at in PGMEA 25° C. 30 wt % solution of 5.0 micrometer Solublewithin 10 minutes polymer 12 in PGMEA and EKC865 at in PGMEA 25° C.

A bonding experiment was then conducted with formulations of polymercompositions 11 and 12. A first adhesive (hereafter referred to asadhesive 1) included polymer 11 in propylene glycol monomethyl etheracetate (PGMEA), wherein polymer 11 composition was present in an amountequal to 35 wt. % solid. A second adhesive (hereafter referred to asadhesive 2) included polymer 12 in propylene glycol monomethyl etheracetate (PGMEA), wherein polymer was present in an amount equal to 30wt. % solid. Each adhesive, i.e., adhesive 1 and adhesive 2, was appliedto substrates, i.e., wafers, for bonding. The deposition process foradhesive 1 included a spin on deposition process at 800 rpm, followed bya bake at 110° C. for approximately 10 minutes, which resulted in adeposited thickness of approximately 12 um. The deposition process foradhesive 2 included a spin on deposition process at 1500 rpm, followedby a bake at 110° C. for approximately 10 minutes, which resulted in adeposited thickness of approximately 5.5 um. Both wafers including thedeposited adhesive 1 and adhesive 2 were then baked at 180° C. for 10minutes. Both wafers, i.e., wafer including adhesive 1, and waferincluding adhesive 2, exhibited a smooth and uniform coating.

The wafers including the applied adhesives, i.e., adhesive 1 or adhesive2, where then bonded to a bonding wafer. The bonding conditions includedthat both wafers, i.e., wafers including adhesive 1 and wafers includingadhesive 2, where bonding to bonding wafers at a temperature of 170° C.for a time period of 1 minute using a 1500 mbr tool pressure.Observation of the bonded structures illustrated that both adhesivecompositions, i.e., adhesive 1 and adhesive 2, provided bonds withoutvoids.

Debonding was not detected using razor blade testing. A razor bladecould not damage, e.g., debond, the edge of the bonded interface. Forexample, a razor blade that is applied to the edge of the bondedinterface could not debond the adhesive, i.e. adhesive 1 or adhesive 2,from the wafer to which the adhesive has been bonded.

Data Set 3

Wafer bond/debond adhesives were also characterized by rheologicalmeasurements to determine the complex viscosity vs temperaturecorrelation. This correlation was used to determine the bondingtemperature. In our case, the temperature at which the complex viscositywas around 750 Pa·s was selected as the bonding temperature.

FIG. 11 is a plot of illustrating complex viscosity (Pa sec) as afunction of temperature for polymeric adhesives composed of styrenemaleimide copolymers. Plot line 200 is viscosity data measured from anadhesive composed of styrene maleimide copolymers designated as Polymer1, Plot line 210 is viscosity data measured from an adhesive composed ofstyrene maleimide copolymers designated as Polymer 2. Plot line 220 isviscosity data measured from an adhesive composed of styrene maleimidecopolymer designated as Polymer 3.

FIG. 12 is a plot of complex viscosity (Pa sec) as a function oftemperature for polymeric adhesives composed of vinyl ether-maleimidecopolymers, Polymer 11, Polymer 12, and Polymer 14 respectively. Thetemperature ranges from 60° C. to 250° C.

While the present disclosure has been particularly shown and describedwith respect to preferred embodiments thereof, it will be understood bythose skilled in the art that the foregoing and other changes in formsand details may be made without departing from the spirit and scope ofthe present disclosure. It is therefore intended that the presentdisclosure not be limited to the exact forms and details described andillustrated, but fall within the scope of the appended claims.

What is claimed is:
 1. An adhesive bonding method comprising: bonding a handling wafer to a front side surface of a device wafer with an adhesive comprising N-substituted maleimide copolymers, wherein the N-substituted maleimide copolymer comprises poly(dodecyl vinyl ether-co-phenylmaleimide); thinning the device wafer from the backside surface of the device wafer while the device wafer is adhesively engaged to the handling wafer; and removing the adhesive by laser debonding, wherein the device wafer is separated from the handling wafer.
 2. The adhesive bonding method of claim 1, wherein the maleimide copolymer composition further comprises maleic anhydride monomer units.
 3. The adhesive bonding method of claim 1, wherein the handling wafer comprises glass.
 4. The adhesive bonding method of claim 1 further comprising forming at least one semiconductor device on the front surface of the device wafer prior to bonding the handling wafer to the device wafer.
 5. The adhesive bonding method of claim 1, wherein the bonding of the handling wafer to the device wafer comprises: applying a layer of the adhesive of the maleimide copolymers on the front surface of the device by spin on deposition; contacting the layer of adhesive with the handling wafer; and curing the adhesive layer at a temperature less than 300° C. under applied pressure ranging from 700 to 2200 millibar. 